Hi and welcome to GoY simple answer Pollylyn is NO particularly as the shreddings will be of green, damp, conifer. On the other hand depending where you have spread it could have an effect on the condition of the soil causing it to be more acidic which could cause distress to sum plants, trees and shrubs.

Shredded pine mulch is combustible and the fire could be very persistent, but I can't recall a single incident where shredded pine mulch has caused a fire. I am a certified fire fighter on Long Island, New York. Just don't take a fire to it or set off fire works near it & keep the BBQ at a safe distance. You should be OK.

Normally, it holds too much moisture to burn easily, but as a precaution, I wouldn't pile it more than 10 cm thick, and hose it down once every two weeks during long dry spells. On the plus side, if you are talking about 'Leylandii' and its kin, it should contain enough cedar oil to repel bugs for a few years.

The resins in a conifer are combustible but in this case there is no concern to be had.

Its used very widely as a mulch in the UK and I've never heard of any fire risk. Assure your other half he can stop worrying! The only risk I can think of would be leaving a glass bottle on it during an extended drought...

Lol Stera!